KABUL, Afghanistan — The United Nations on Monday said that suspected Taliban detainees are routinely beaten and tortured in detention centers run by Afghanistan's police and spy agency.

The U.N. said it based its findings on interviews conducted with 379 pre-trial detainees and convicted prisoners at 47 detention centers in 22 provinces between October 2010 to August 2011.

The 74-page report said the interviews uncovered evidence of "the use of interrogation techniques that constitute torture under international law and crimes under Afghan law, as well as other forms of mistreatment."

It said beating and torture was applied "systemically" in detentions centers run by the National Directorate of Security, Afghanistan's spy agency.

Forty-six percent of 273 detainees interviewed in the Afghan spy agency's detention centers told U.N. interviewers that they had been subjected to different forms of torture while the were interrogated. The abuse often included sexual humiliation.

Beyond physical mistreatment, many prisoners also said they had been held beyond the maximum allowed by law and denied family visits, the report said.

"Electric shock, twisting and wrenching of detainees' genitals, stress positions including forced standing, removal of toenails and threatened sexual abuse were among other forms of torture that detainees reported," the report said.

The U.N. said it had taken into consideration Afghan government concerns that prisoners might lie about their treatment to discredit the police and security forces.

Afghanistan's interior minister, Bismillah Khan Mohammedi, the head of the National Directorate of Security, denied the allegations last month when word of the report's likely findings were leaked. A statement issued then said the Afghan government "made sure human rights are respected and prisoners are not mistreated."

But the United States-led International Security Assistance Force, or ISAF, last month stopped transferring detainees to Afghan detention facilities and is now negotiating with the Afghan government ways to monitor the treatment of detainees in Afghan custody. It is a violation of international law for one country to surrender a prisoner to another if it is likely that prisoner will be tortured.

ISAF said the U.N. told it of its findings last month and that since then has been working with the Afghan government on a six-stage plane to improve conditions in prisons, including inspections, monitoring, training in human rights protection, and formal certification procedures.

"Initiatives being implemented will help strengthen rule of law, continue to enhance government credibility, and limit the appeal of the insurgency," ISAF said in a statement.

Canada and Great Britain also have stopped surrendering Taliban suspects to Afghan authorities, the U.N. report said.